Light emitting device

ABSTRACT

A light emitting device includes a base; a plurality of semiconductor laser elements disposed on the base and configured to emit light laterally from the plurality of semiconductor laser elements; a reflecting member disposed on the base and configured to reflect light from the semiconductor laser elements; a surrounding part disposed on the base and surrounding the semiconductor laser elements and the reflecting member; a wiring part disposed on the base so as to extend to a location outside of the surrounding part; a radiating body disposed on the surrounding part and having an opening; and a wavelength converting member that is located in the opening of the radiating body, the wavelength converting member being configured to convert a wavelength of light that is emitted from the plurality of semiconductor laser elements and reflected upward by the reflecting member.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/775,432 filed on Jan. 29, 2020, which is a continuation ofU.S. patent application Ser. No. 16/103,879, filed on Aug. 14, 2018 (nowU.S. Pat. No. 10,587,091), which is a continuation of U.S. patentapplication Ser. No. 14/689,984, filed on Apr. 17, 2015 (now U.S. Pat.No. 10,079,470), which claims priority to Japanese Patent ApplicationNo. 2014-086931, filed on Apr. 18, 2014, the entireties of which arehereby incorporated by reference.

BACKGROUND 1. Field

The present disclosure relates to a light emitting device.

2. Description of the Related Art

Conventionally, a light emitting device provided with a plurality ofsemiconductor laser elements (LD 16) and a wavelength converting member(fluorescent body layer 65) on a base (radiator 17) has been proposed(refer to Japanese Patent Application Laid-open No. 2012-22802).

SUMMARY

An object of the present disclosure is to provide a light emittingdevice with high heat dissipation performance.

A light emitting device includes: a base; a plurality of semiconductorlaser elements that are disposed on the base and that are configured toemit light laterally from the plurality of semiconductor laser elements;a reflecting member that is disposed on the base and configured toreflect light from the plurality of semiconductor laser elements; asurrounding part that is disposed on the base and that surrounds theplurality of semiconductor laser elements and the reflecting member; awiring part that is disposed on the base so as to extend to a locationoutside of the surrounding par, the wiring part being electricallyconnected to the plurality of semiconductor laser elements; a radiatingbody disposed on the surrounding part, the radiating body comprising atleast one of a metal and a ceramic, and the radiating body having anopening; and a wavelength converting member that is located in theopening of the radiating body, the wavelength converting member beingconfigured to convert a wavelength of light that is emitted from theplurality of semiconductor laser elements and reflected upward by thereflecting member.

Deterioration of semiconductor laser elements and deterioration of awavelength converting member can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic perspective view of a light emitting deviceaccording to a first embodiment, FIG. 1B is a schematic exploded view inFIG. 1A, and FIG. 1C is a schematic end view taken along a line A-A inFIG. 1A;

FIG. 2A is a schematic perspective view of a light emitting deviceaccording to a second embodiment, FIG. 2B is a schematic exploded viewin FIG. 2A, and FIG. 2C is a schematic end view taken along a line A-Ain FIG. 2A; and

FIG. 3A and 3B are a cross-sectional view and a plan view, respectively,showing an example of a light emitting device including a heat sink.

DETAIL DESCRIPTION [Light Emitting Device 1 According to FirstEmbodiment]

FIG. 1A is a schematic perspective view of a light emitting device 1according to a first embodiment, FIG. 1B is an schematic exploded viewin FIG. 1A, and FIG. 1C is a schematic end view taken along a line A-Ain FIG. 1A. In FIG. 1A, portions of members are transparently shownusing dashed lines in order to facilitate understanding.

As shown in FIGS. 1A to 1C, the light emitting device 1 includes: a base10; a plurality of semiconductor laser elements 20 that are disposed onthe base 10 and that are configured to emit light laterally from theplurality of semiconductor laser elements; a reflecting member 70 thatis disposed on the base 10 and configured to reflect light from theplurality of semiconductor laser elements 20; a surrounding part 30 thatis disposed on the base 10 and that surrounds the plurality ofsemiconductor laser elements 20 and the reflecting member 70; a wiringpart 40 that is disposed on the base 10 so as to extend to a locationoutside of the surrounding part 30, the wiring part being electricallyconnected to the plurality of semiconductor laser elements 20; aradiating body 50 disposed on the surrounding part, the radiating bodycomprising at least one of a metal and a ceramic, and the radiating bodyhaving an opening 51; and a wavelength converting member 60 that islocated in the opening 51 of the radiating body 50, the wavelengthconverting member being configured to convert a wavelength of light thatis emitted from the plurality of semiconductor laser elements 20 andreflected upward by the reflecting member 70.

When a light emitting device includes a plurality of semiconductor laserelements, discharge of heat generated at each of the semiconductor laserelements from a base is inhibited. Therefore, heat is likely toaccumulate in the semiconductor laser elements and, as a result, thesemiconductor laser elements deteriorate faster.

In consideration thereof, in the light emitting device 1, each of thesemiconductor laser elements 20 is arranged on the base 10 so that lightis emitted to the side in a lateral direction. Accordingly, sincedistances from the semiconductor laser elements 20 to the base 10 arereduced and heat radiation performance is improved, deterioration of thesemiconductor laser elements 20 can be suppressed.

In addition, when a light emitting device includes a plurality ofsemiconductor laser elements, since light emitted from the plurality ofsemiconductor laser elements enters a wavelength converting member, theamount of heat generated at the wavelength converting member increases.As a result, the wavelength converting member deteriorates faster. Inconsideration thereof, in the light emitting device 1, the wavelengthconverting member 60 is provided on the radiating body 50 containing atleast one of metals and ceramics. Accordingly, since heat generated atthe wavelength converting member 60 can be released using the radiatingbody 50, deterioration of the wavelength converting member 60 can besuppressed.

Hereinafter, primary members and the like of the light emitting device 1will be described in order.

(Light Emitting Device 1)

The light emitting device 1 can be preferably used as, for example, asurface-mounted light emitting device.

(Base 10)

As the base 10, a member containing ceramics such as aluminum nitrideand aluminum oxide can be used.

Heat generated by the plurality of semiconductor laser elements 20 isreleased via the base 10.

(Plurality of Semiconductor Laser Elements 20)

The plurality of semiconductor laser elements 20 are arranged on thebase 10 so that light is emitted to the side.

The semiconductor laser elements 20 may be directly provided on the base10 or may be provided on the base 10 via a sub-mount Example of materialof sub-mount can be provided by aluminum nitride or silicon carbide.

Nitride semiconductor laser elements or the like can be used as thesemiconductor laser elements 20.

Light emitted to the side by the plurality of semiconductor laserelements 20 is reflected by the reflecting member 70, changes itsdirection to upward, and enters the wavelength converting member 60provided in the opening 51 of the radiating body 50.

As shown in FIG. 1B, since the semiconductor laser elements 20 areprovided so that main surfaces thereof face the base 10, heat from thesemiconductor laser elements 20 can be efficiently discharged via thebase 10. Either of an n electrode or a p electrode is provided on themain surface (lower surface of the semiconductor laser elements 20 inFIGS. 1A to 1C) of the semiconductor laser elements 20 on the side ofthe base 10, and the electrode is electrically connected to the wiringpart 40, for example, via a sub-mount.

In addition, a main surface (upper surface of the semiconductor laserelements 20 in FIGS. 1A to 1C) opposite to the main surface (lowersurface of the semiconductor laser elements 20 in FIGS. 1A to 1C)described above is provided with the other electrode of an n electrodeand a p electrode, and the electrode is electrically connected to thewiring part 40, for example, via a metal wire.

The number of semiconductor laser elements 20 to be provided in onelight emitting device 1 is at least 2 or more and can be, for example,10 or more. By increasing a package size, around 10 to 100 semiconductorlaser elements 20 can be provided in one light emitting device 1.

When arranging a plurality of semiconductor laser elements 20 on oneside of the reflecting member 70, a distance between adjacentsemiconductor laser elements 20 can be set to, for example, 200 μm ormore and 1000 μm or less.

(Reflecting Member 70)

The reflecting member 70 is a member that reflects light from theplurality of semiconductor laser elements 20 toward the wavelengthconverting member 60 and which is provided on the base 10.

A shape of the reflecting member 70 is not particularly limited.

For example, when the reflecting member 70 is positioned between aplurality of semiconductor laser elements 20, a member with anapproximately triangular prism shape (with a triangle-like trapezoidalsection) as shown in FIG. 1A to 1C or the like can be used as thereflecting member 70.

As the reflecting member 70, for example, optical glass made ofsynthetic quartz or the like in which a portion to be irradiated bylaser light is provided with a reflective film can be used.

Since such members exhibit high heat resistance, the members can be usedwith less deterioration even when irradiated with light from theplurality of semiconductor laser elements 20.

As the reflective film, a metal film made of silver, aluminum, or thelike or a dielectric multilayer film in which oxide films of siliconoxide or tantalum oxide or the like are laminated can be used.

(Surrounding Part 30)

The surrounding part 30 is provided on the base 10, and surrounds theplurality of semiconductor laser elements 20 and the reflecting member70.

Accordingly, since light output of the plurality of semiconductor laserelements 20 is prevented from declining due to optical dust collectionor the like, the life of the light emitting device 1 can be prolonged.

Ceramics or metals such as iron can be used for the surrounding part 30.

(Wiring Part 40)

The wiring part 40 is provided on the base 10 so as to extend to theoutside of the surrounding part 30, i.e., to the outside of a peripheraledge of the surrounding part 30.

Accordingly, since the wiring part 40 need not be arranged below thebase 10, an entire lower surface of the base 10 can be used as a heatradiating surface.

In other words, heat generated by the plurality of semiconductor laserelements 20 is released via the base 10 in an efficient manner.

The wiring part 40 is electrically connected to the plurality ofsemiconductor laser elements 20.

By energizing the wiring part 40, power can be supplied to the pluralityof semiconductor laser elements 20.

The wiring part 40 is divided into an anode (p electrode side) and acathode (n electrode side).

While the anode and the cathode are extracted outward in differentdirections in the light emitting device 1 shown in FIGS. 1A to 1C, theanode and the cathode may alternatively be extracted in a samedirection.

(Radiating Body 50)

The radiating body 50 is provided on the surrounding part 30.

By constructing the radiating body 50 and the surrounding part 30 withseparate members, since a heat radiating path of the wavelengthconverting member 60 can be more readily secured separately from a heatradiating path of the semiconductor laser elements 20, heat generated atthe wavelength converting member 60 is efficiently radiated via theradiating body 50.

The radiating body 50 may be directly provided on the surrounding part30 (refer to FIGS. 1A to 1C) or may be provided on the surrounding part30 via another member (refer to FIG. 2A to 2C).

The radiating body 50 can be connected to the surrounding part 30 oranother member provided between the surrounding part 30 and theradiating body 50 using AuSn, low-melting point glass, or the like.

A material with a thermal conductivity of 100 W/mK or more is preferablyused for the radiating body 50.

For example, materials with high heat radiation performance includingmetals such as copper and aluminum, ceramics such as an AlN sinteredbody and a SiC sintered body, or a combination of such metals andceramics are used.

The radiating body 50 has an opening 51.

The plurality of semiconductor laser elements 20 are surrounded by thesurrounding part 30 which reflects light emitted from the plurality ofsemiconductor laser elements 20. The light emitted from the plurality ofsemiconductor laser elements 20 is emitted to the outside of thesurrounding part 30 by passing through the opening 51 of the radiatingbody 50 provided above the surrounding part 30. Therefore, in the lightemitting device 1, an opening plane of the opening 51 constitutes alight emitting plane.

A shape of the opening 51 of the radiating body 50 is not particularlylimited.

Examples of the shape of the opening 51 may include a cylinder, atruncated cone, a pyramidal frustum, and a rectangular parallelepiped.

Although not particularly limited, the opening 51 of the radiating body50 preferably has an inner surface that is inclined such that theopening plane thereof becomes wider as it goes upward.

Accordingly, light extraction efficiency of the light emitting device 1is improved.

Examples of such a shape include an inverted truncated cone and aninverted pyramidal frustum.

A reflective film can be provided on an inner surface of the radiatingbody 50.

Accordingly, since light absorbed by the radiating body 50 can bereflected by the reflective film, light extraction efficiency isimproved.

As the reflective film, metals including Au, Ag, or Al can be used.

The wavelength converting member 60 is preferably provided inside theopening 51 of the radiating body 50.

In this case, the opening 51 of the radiating body 50 can be formed sothat a peripheral edge thereof is farther inward than a peripheral edgeof the surrounding part 30.

Accordingly, high-output light can be emitted without increasing a sizeof the light emitting plane. Furthermore, by concentrating light emittedfrom the plurality of semiconductor laser elements 20 on the wavelengthconverting member 60, light with high luminance can be emitted from thewavelength converting member 60.

The radiating body 50 is formed in, for example, a flat plate shape.Accordingly, a heat sink or the like can be readily provided on an uppersurface of the radiating body 50.

In addition, when the radiating body 50 has a flat plate shape, theopening 51 of the radiating body 50 (wavelength converting member 60) ispositioned closer to the reflecting member 70 compared to a case where,for example, the radiating body 50 has a curved plane shape or theradiating body 50 has irregularities.

Accordingly, since light emitted from the plurality of semiconductorlaser elements 20 enters and exits the wavelength converting member 60before the light is completely diffused, the light emitting plane of thelight emitting device 1 can be reduced and light with high luminance canbe extracted from the light emitting device 1.

The peripheral edge of the radiating body 50 is positioned fartheroutward than, for example, the peripheral edge of the surrounding part30.

Accordingly, heat of the wavelength converting member 60 can be morereadily diffused.

A thermal conductivity of the radiating body 50 can be set higher than athermal conductivity of the surrounding part 30.

Accordingly, since radiation via the radiating body 50 of heat generatedat the wavelength converting member 60 is promoted, a decline inconversion efficiency of the wavelength converting member 60 due to heatcan be suppressed.

While an area of an upper surface of the radiating body 50 may be equalto an area of an upper surface of the base 10, the area of the uppersurface of the radiating body 50 may be greater than the area of theupper surface of the base 10.

When the area of the upper surface of the radiating body 50 is greaterthan the area of the upper surface of the base 10, heat generated at thewavelength converting member 60 is more readily discharged via theradiating body 50 than in a case where the area of the upper surface ofthe radiating body 50 is equal to the area of the upper surface of thebase 10.

(Wavelength Converting Member 60)

The wavelength converting member 60 is provided in the opening 51 of theradiating body 50.

After being reflected by the reflecting member 70, the light emittedfrom the plurality of semiconductor laser elements 20 enters thewavelength converting member 60, whereby a part of the light issubjected to wavelength conversion and then emitted from the wavelengthconverting member 60.

The wavelength converting member 60 preferably has a plate shape.

While the wavelength converting member 60 may be provided in plurality,a single wavelength converting member 60 is provided as shown in FIG. 1Aand the like in order to obtain light with high luminance.

A transmissive member containing a fluorescent body or the like can beused for the wavelength converting member 60.

In this case, the light emitted from the plurality of semiconductorlaser elements 20 excites the fluorescent body contained in thetransmissive member. As a result, light with a different wavelength fromthe light emitted from the plurality of semiconductor laser elements 20is emitted from the fluorescent body and outputted from the transmissivemember.

Non-coherent light is an example of light emitted from the wavelengthconverting member 60.

When semiconductor laser elements emitting blue light are used as thesemiconductor laser elements 20, a fluorescent body that emits yellowlight using excitation light from the semiconductor laser elements 20can be used.

In this case, the light emitted from the wavelength converting member 60is white light that is a mixture of blue light and yellow light.

Examples of a fluorescent body emitting yellow light include a YAGfluorescent body, a TAG fluorescent body, and a strontium silicatefluorescent body.

In addition, an inorganic member is preferably used as the transmissivemember. For example, aluminum oxide, silicon oxide, titanium oxide,glass, or the like can be used.

Accordingly, the wavelength converting member 60 can be given highresistance to heat and light.

In the present embodiment, a sintered body of a YAG fluorescent body andaluminum oxide is used as the wavelength converting member 60.

A filter 80 which transmits light emitted from the plurality ofsemiconductor laser elements 20 and reflects light subjected towavelength conversion at the wavelength converting member 60 may beprovided below the wavelength converting member 60.

Accordingly, since the light extraction efficiency of the light emittingdevice 1 is improved, light with even higher luminance can be extractedfrom the light emitting device 1.

As the filter 80, for example, a member with reflectance of 90% orhigher with respect to light which has a predetermined wavelength (lighthaving a same wavelength as the light emitted from the plurality ofsemiconductor laser elements 20) and which enters at an incidence angleof 45 degrees or more can be used.

A part of light entering the wavelength converting member 60 from underthe wavelength converting member 60 (light emitted from the plurality ofsemiconductor laser elements 20) is reflected inside the wavelengthconverting member 60 and which attempts to exit the wavelengthconverting member 60 in a downward direction.

However, by using the member described above as the filter 80, suchlight is efficiently reflected by the filter 80 and returned to theinside of the wavelength converting member 60.

As a result, the light extraction efficiency of the light emittingdevice 1 is improved and light with even higher luminance can beextracted from the light emitting device 1.

(Heat Sink)

An upper surface of the radiating body 50 can be connected to a heatsink.

Accordingly, heat radiation performance of the light emitting device 1as a whole is improved.

In addition, even in a case where heat dissipation is difficult througha path from lower surface of radiating body 50 to surrounding part 30due to low thermal conductivity of the surrounding part 30, heatdissipation can be performed through a path from upper surface ofradiating body 50 to heat sink.

[Light Emitting Device 2 According to Second Embodiment]

FIG. 2A is a schematic perspective view of a light emitting device 2according to a second embodiment, FIG. 2B is a perspective exploded viewin FIG. 2A, and FIG. 2C is a perspective end view taken along a line A-Ain FIG. 2A.

In FIG. 2A, portions of members are transparently shown using dashedlines in order to facilitate understanding in a similar manner to FIG.1A.

As shown in FIG. 2A to 2C, the light emitting device 2 according to thesecond embodiment differs from the light emitting device 1 according tothe first embodiment in that a cap 90 having an opening 91 is providedbetween the surrounding part 30 and the radiating body 50.

The opening 91 of the cap 90 is provided so that the opening 91 of thecap 90 at least partially overlaps with the opening 51 of the radiatingbody 50 so as to enable light to be emitted from the opening 51 of theradiating body 50.

With the light emitting device 2 according to the second embodiment, amaterial with high heat radiation performance can be used in theradiating body 50 while ensuring airtightness with the cap 90.

The opening 91 of the cap 90 is preferably provided with a sealingmember 100 as shown in FIG. 2A to 2C.

Accordingly, the plurality of semiconductor laser elements 20 can behermetically sealed.

As a result, since a decline in output due to optical dust collection orthe like is further suppressed, the life of the light emitting devicecan be further prolonged.

A transmissive member such as ceramics and glass can be used as thesealing member 100.

In order to provide hermetic sealing, preferably, the cap 90 and thesurrounding part 30 are welded together. To this end, preferably, theentire cap 90 or at least an end portion of the cap 90 on a side incontact with the surrounding part 30 and the entire surrounding part 30or at least an end portion of the surrounding part 30 on a side incontact with the cap 90 are constructed from metal members.

Known materials can be used as a material of the cap 90.

For example, when the cap 90 and the surrounding part 30 are to bejoined together by welding, a material with weldability such as kovarcan be used as the material of the cap 90.

In addition, when the cap 90 and the surrounding part 30 are to bejoined together by AuSn or low-melting point glass, ceramics or metalsother than kovar can be used as the material of the cap 90.

Joining the cap 90 and the surrounding part 30 by welding only at jointportions, it is possible to join the cap 90 and the surrounding part 30without causing thermal deterioration of the semiconductor laserelements 20 and the like.

(Heat Sink)

FIG. 3A and 3B are a sectional view and a plan view, respectively,showing an example of a light emitting device including a heat sink.

In FIG. 3B, illustration of radiating fins 55 is omitted to makepositions where temperature regulators 56 are arranged easilyrecognizable.

As shown in FIG. 3A and 3B, the heat sink includes the radiating fins 55and the temperature regulators 56.

The radiating fins 55 are constructed from, for example, aluminum orcopper.

In addition, the temperature regulators 56 are constituted by, forexample, Peltier elements.

As shown in FIG. 3A and 3B, the light emitting device may furtherinclude a heat radiating platform 57.

The heat radiating plate 57 is connected to, for example, an entirelower surface of the base 10.

Accordingly, heat generated by a plurality of semiconductor laserelements 20 is more easily discharged to the heat radiating plate 57.

While embodiments of the present invention have been described above,the description merely represents examples thereof and is not intendedto limit the configurations described in the claims in any waywhatsoever.

EXPLANATION OF REFERENCE NUMERALS

1 Light emitting device

2 Light emitting device

10 Base

20 Semiconductor laser element

30 Surrounding part

40 Wiring part

50 Radiating body

51 Opening of radiating body

55 Radiating fin

56 Temperature regulator

57 Heat radiating plate

60 Wavelength converting member

70 Reflecting member

80 Filter

90 Cap

91 Opening of cap

100 Sealing member

What is claimed is:
 1. A light emitting device comprising: a pluralityof light emitting elements comprising at least a first light emittingelement and a second light emitting element; a base on which theplurality of light emitting elements are disposed, and the basedissipating heat from the plurality of the light emitting elements; asurrounding part that surrounds the plurality of light emitting elementsin a top view; a wavelength converting member having a plate shapedisposed between the first light emitting element and the second lightemitting element in the top view, light from the first light emittingelement and light from the second light emitting element are incident onthe wavelength converting member, and a plurality of wiring partscomprising at least one first wiring part and at least one second wiringpart, the plurality of wiring parts being electrically connected to thefirst light emitting element and the second light emitting element viawires, wherein the first light emitting element, the wavelengthconverting member and the second light emitting element are disposed ina first direction in the top view, at least one of the first lightemitting element and the second light emitting element is disposedbetween the at least one first wiring part and the at least one secondwiring part in a second direction, and the second direction isperpendicular to the first direction.
 2. The light emitting deviceaccording to claim 1, further comprising: a light reflecting memberdisposed between the base and the wavelength converting member.
 3. Thelight emitting device according to claim 2, wherein the light reflectingmember disposed between the first light emitting element and the secondlight emitting element in the top view.
 4. The light emitting deviceaccording to claim 2, wherein at least a portion of the light from thefirst light emitting element and/or at least a portion of the light fromthe second light emitting element is reflected by the light reflectingmember, and at least a portion of the light reflected by the lightreflecting member is wavelength converted by the wavelength convertingmember.
 5. The light emitting device according to claim 1, wherein thewavelength converting member is disposed above the plurality of lightemitting elements.
 6. The light emitting device according to claim 1,wherein the base is ceramic.
 7. The light emitting device according toclaim 1, wherein the surrounding part is ceramic.
 8. The light emittingdevice according to claim 1, wherein at least a portion of the lightfrom the first light emitting element and/or at least a portion of thelight from the second light emitting element is incident on a lowersurface of the wavelength converting member.
 9. The light emittingdevice according to claim 1, wherein an uppermost point of the firstlight emitting element is higher than the plurality of wiring parts. 10.The light emitting device according to claim 1, further comprising: acover disposed on the surrounding part such that the plurality of lightemitting elements are hermetically sealed.
 11. The light emitting deviceaccording to claim 10, wherein the wavelength converting member isdisposed on the cover.
 12. The light emitting device according to claim11, the cover comprises a cap having an opening and a sealing membercovering the opening of the cap.